Electrical regulating system



Aug. 11, 1942. L. H. PERRY ETAL 3 ELECTRICAL REGULATING SYSTEM FiledSept. 20, 194C inventors: Leo H. erry, Herman Bang Their Attorneg.

' f UNITED; isTATE 1 generator Ilating to .-.controlling s ns "8 3mm? Vquiredthat the generator may one windingeidle and with ed er-that therespective windings may :be dperwithdifierent percentage Y. one ortheprovide a regulating egenerators so thatv suchgenerators may be operatedwithpredeterof our invention,

volt-ampere relay,

Patented Aug. 1.1, 1942 "uncrit cal.- nnoum'r uoysrs'rnm Leo H; Perry,

--=Electric Company, a corporationnf New :Yo'r'kl I 20, iocuims. (c1. m-lie.)- I

: f ApplicationScptcmber bur invention relates'to electrical regulating"systems Iondynamo-electricmachines and more lparticularlyrto loadregulating I natingcurrentzgenefatora, I l

tion is,applic ablefor use in c aspectsinconnection with'a'plurality-ofV,

V .it-is, particularly applicable n -and-iwi1I- .be-:qescribed,.by wayof illustration, in "a.nd the equipment preset, by connectionudoublewinding generatorsj-conunectedvingasectionalized bus'systein. I

systems for. altercommercial use of theother windingloadatedslmultaneously but doubleyvi'nding syn- I 7 presentedSchenectady, N. Y., @Lansdowne, .Pa.,

prime mover is- :and .Herman assignors to .General controlled to efiectu load reductionflin incrementsuntil the load -:on the givengenerator'winding'is'reduced to-"a predetermined loadings. most-casesindependent loading of .other winding, 61' k the respective windings,must be hmited to predetermined values; otherwise,

temperatures.

new and improved regulating system for .dynamo-electricmachines.

.It is another obiect of our invention to provide an-irnproved loadregulating system for a pluralitylo't -synchronous generator. circuits.

It is a further object of our. invention to prov'ide an improved loadregulating system for synchronous generators It is a still furtherobject of our invention .to

system for 'double-winding of the double-winding'type.

the respective windings of mined unequal loadings without subjecting themachine to harmful operating Conditions.

.over 'a predetermined value, suchvas fifty-five per cent'oithegenerator rating for a certain" time interval, a load back-off equipmentis put into operation. The field excitation of the generator unequalloading of ,25 there 'is danger. of injuring :the:.insulationoiJthe-machin'e due to the development of excessive.Itis-anobjectoi our invention to provide a "-or less'than'the tion ofthesload back-off equipmentis-fte'rminated 1o Ourinvention'will-bebetterunderstood by reference to the 19110 its scope windingsdur'ingfthe varivalue within a predetermined time.* 'When the current inthe overloadedwinding is reduced to predetermined value, the operav g Vtthe ope'rator for controlunder the voltage r l; :governorsettin'gj wwing description taken in connection with*the accompanyingdrawing; and Uwill "be pointed out' 'in theappended j1aims f "The single figure of theaccompanying-drawing {is a diagramrnatic illustration of :an embodiment*three phase v n generator-connected 'a' section'alized 'bus andoperated by a :prime mover. a?

Referring-1o the drawing; a-ithree-phase :=dou ble-winding synchronous*generator l :having a :a plurality of separately insulated statorwindings 2 and '3 is=conn'ect'ed:to energizeamain bus '4; "The'busjliss'hown as comprisingtw sections '5 and i1lustrated;:the"generator-winding 2 bus-section a5 and the is connected -.to energize generatorwlndingj is connected-to energize. bus

"section 6! *It will; of

I course be'-understood by those skilled in the art that othersynchronous generators (not shown) are connected to the main bus 4 'for"operation in' parallel; with generator -l;' The generator -"I isprovided-with an excitation-- circuit indicated by the rotatable fieldwinding f 'a ed to '=be=driven by a Suitable y r' irsuch'as a'steamzturbine.

' The prime mover 8 is supplied'mith operating having a self-excitedfield is normally controlled by a voltage regulator but the loadback-off equipment transfers. the field excitation 'controlfromthevoltage-regulator to i factor on the genfluid through a valve-or gate 29maintainedin a. position dependent upon an "operating condition of theturbine 'by'means ofa governor UL Means are provided to change =theadjustment-of the governor mechanism such as by asynchronizing mechanism'1 I connected tobeoperated in either direction by'a'reversibl'e pilotmotor 12. The pilot motor i2 .is provided with *field windings l3 and .Mwhich are connected'to be energized selectively from a control bus 15 bythe regulating mechanism to' be described presently.

- The field winding 1 of generator vI is arranged to be energized by 'adirect current exciter. l8 winding ILalthough obviously the well knownpilot exciter excitation system'could'be used if desired. Amotor-operated rheostat 18 is connected in circuit with field winding"l1 and is'arranged to be operated by areversible pilot motor I9 havingfield windings '20 and 2| which are arranged to be energized selectivelyfor raising orlowering the voltage of exciter Hi. The exciter i6 isalso'provided torand :manual' speed contactors 22 and 23 are normallycontrolledby-a-voltage regulator indicated generally at=25. A suitablevoltage regulator is of the typedescribed and claimed in Patent No..

1,848,852, granted March 8, 1932, on an application, of L. W. Thompson.This regulator is provided-with a.voltage. responsive operating element;illustrated as representing a three-phase 7 torquemotor fli. Inordertocontrol the excitation of the generator I to maintain the average valueof the voltages of the windings 2 and 3 at aspredetermined value,the-torque motor 26 is 7 -connected..- to;be energized from each ofthebus sections. 5 and 6 througha potential transformer 21 connected to bus5 and potential transformer -28 connected to bus 5., The secondarywinding of transformer 21 is connected through an impedance 29 and thesecondary winding of trans- 7 former.=28is connected through animpedance 30 to a common circuit, 3l to which the windingsof the torquemotor 26 are connected. With equal impedances, particularly with a highresistance: component', the torque motor 26 responds to the averagevoltageof the buses 5 and 6.

If .desired,

'contacts 49.

cordance with the loading of the several generator-windings, we providecurrent transformer 41 in a phase'conductor' of generator winding 2 andanother current transformer 42 in a phase conductor of generator winding3. Current transformer 4| is connected to energize the operating coil ofa current limiting relay 43 which is pro vided with normally closedcontacts 45 and nor- 'mally open contacts 46. Current transformer 42is-c'onnected to energize the operating coil of a current limiting.relay 41 which is provided with normally closed contacts 48 and normallyopen The current limitirg relays 43 and 41 control multi-contactauxiliary relays 50 and 51 respectively to provide a sufficient numberof contacts to perform the necessarycontrol' functions. The operatingcoil'of auxiliary-relay 50 is arranged to be energized from the controlbus 15 when therelay 43 is energized to closeits normallyopen contacts46.; Similarly; theioperating coil of auxiliary relay 5| is arrangedtb'be-energized whenthenormally open contacts 43-of relay 41 are closed.The relayf50 is provided with noi nally closed contacts'52 and normally"open contacts 53 53', 54 and 55;, The relay 51 is provided withnormally closed contacts 55'and normally open contacts 51, 58,58 and 53.*If both therelayS 43'and '41 are picked up'both the relays 50 and 5|are picked up and no circuit can be made to startlthe operation oftheload back-off jcquipment j However, if one of the relay: or

the. impedances 29 and 30 may be selected or Q F adjusted to be ofdifferent values so as to hold a voltageintermediate to the voltages ofbuses 5 and 6, other than the average voltage.

The=torque, m otor 26.:is arrange'dto operate contacts which areidentified, respectively, as the slow speed raise and flower contacts 32and 33 and highvspeed raise and lower contacts 34 and 35. The highs'peed raise" and lower contacts 34 and control the high speedcontactors Hand 23, respectively. Contacts 32 and .33 cooperate with acommon center contact 36 I having-a notched circular form, and contacts34 The apparatus just described will function to hold a constant averagevoltage between the bus sections 5 and 5 but there is no limitation onthe current loading of either winding. In accordance with our invention,we provide equipment referred to herein as load back-off equipment to.

reduce the load. on the generator whenever the 1 current carried byeither of the windings, but not both, exceeds a predetermined value. aA' common commercial current limit is 55 per cent of the generatorrating and for purposes of simplifying the description, thepredetermined current limit will be referred to as 55 per cent of thegenerator rating. In order to obtain response in ac- '41 and theassociated auxiliary re1ay50 or 5| is picked'up, a circuitis completedtoenergize the control relaytfli Relay 60 is provided 'witlra pair ofnormally open contacts 'SI and i s also-provided with time delay closingmeans indicated 'by the dashpot 82 which may {be adjustable from severalseconds up to thirty seconds, depending upon the nature of the-system.This time delay is for the purpose of preventing false operation of theload'back-off equipment on system faultsi- 'Nor mally, such faults willhave'had ample 'opportunity to clear in thirty seconds or less. closing'of contacts 6% of relay "50 energizes the operating coil of a handreset relay 63. The hand reset mechanism is indicated by the manuallyoperated latch'B4; Relay 63 is provided with normally closed contacts65-,65, 61 and '68 and J normally open contacts 69, 10, 1i and "H'.-When relay 63 picks" up it'latches in and transfers control from thevoltage regulator 25 too. reactive volt-ampere relay 12 or 13. Althoughvarious types of reactive volt-ampere relays may be used, a satisfactorytype comprises the double-throw relay '12 which has one potential coil14, one current coil 15 and'a movable contact 16'which floats betweentwo sets of fixed contacts 11 and11' at unity power. The relay would bedesigned to have maximum torqueat zero phase angle between the currentin its currentwinding' and'the potential across its potential winding.With ,this

type, of relay,"it is only necessary to use the usual'quadratureconnection so that the potential coil. 14 is connected through potentialtransformer 18 to two lines of the bus 5 and the cur rent winding 15 is'connected through current transformer 41 in generator winding 2- to theremaining conductor of the three phase'circuit. Similarly, relay '13comprises a double-throw relay which has a potential coil 19, a'currentcoil and a movable contact 8| which floats between two sets of fixedcontacts 82 and 82. The potential coil 19 is connected to two lines ofthe bus 6 through a potential transformer 83 and the current coil 80 isconnected through current The transformer 42 in, generator winding to,theremaining conductor of thethree phase-circuit.

'In order to assure proper operation otthe regulating equipment underload swings occur ring during the operation of the load back-oilequipment, we provide relays 84 and 85. R elay 84 is provided withnormally open contacts 86 occurs under his supervision in a temporaryemergency and no automatic corrective action is taken.

,However, if eitherone of the relays .43 or 41 (but not both) isenergized, relay 60 is energized.

and 81 and relay 85 is provided with normally open contacts 88.-and 89..The contacts of relays 84 and 85 are addedsothatthese devicesin'conjunctionwith relays 5ll and -5I :actually control pilotmotor.l2.'- I a We controlthe field excitationcontrol appa- 'ratusintermittently v oruin small- -incr ements through notching :relays 90and BI which are controlled through the contactsof 50- and ;5I.

' Relay 90 is provided with normally -closed-contacts 92 and time delayclosing meansindicated b the dashpot s3. Relay SI is provided withnormally open contacts 9| and 95 and with-time delay opening pot Q5, v

means indicated by the dash- "Wealso provide means to decrease thepowerinput to the prime mover intermittently or in increments so that theload on theoverloaded :Assume relay:"4 3 has picked up. Then,aspreviously. explained,}relay 50 Wi1l'pick"up and will ..close'itsnormally open contact 54; A' circuit isthen completedfromithe positiveside of bus through.contact 54;. contact 56 of 'relay 5I,

. the operating coil ,of relay fi mj back to the nega- .flyqlsiqggqf puj ls If relay 4 3 ;drops out-be- ..fore. the expiration oftheclosingtime delay of relay.8Il then relays 60 will be reset to itsdeenergized position'" However, if "rela'yj3 remains in its. pickcdt l.pQsitioni ntil the time delay of relay (ill has,.expiried, its.contacts 6I"will close and the operati'oxif of'ithje load back-offequipa merit isinitia'tedj A'lsimilar'sequence of events will occur ifrelay'll picks up and relay is not picked up.

The closing oi'1contlact sl f5l 'of relay; 60 ener'gize's the operatingcoil oi hand: reset relay 63 through the) previously de'scribed circuitcompletednbythe ccntacts :Qfl relays '50 and 5l so winding" maybe'reduced to a predeterminedvalue suchas the previously mentioned -55.;per cent value in a-predetermined time. fln'orderito Drovlde thisincremental. un1oading,- we provide electric bell, is arranged-tobeenergized from the control bus I5 through 'thevnormallyopen contacts 54of relay or the normally open contacts 51 of relay'5I.

'mal load conditions.- -If thecurrent in either having normally, opencontacts in circuit-with A control switch- I06 the raise and lower.circuitsof governor control motor I2 is provided forefiecting manualcontrol.

' The operation of the apparatusas illustrated in the drawing issubstantially as follows: It I will be assumed that the various relaysand control devices are in the illustrated positions and" the variouscontrol relays, except as otherwisev noted, are in the deenergizedposition. From the foregoing description, it is not believed necessaryto give any further description with respect to the operation of thesystem under nor-' generator winding 2 or 3 exceeds the predeter-,-;-

mined value of current, for example, per centv of the generator rating,the relay 43 or 41 is energized and a circuit from bus I5 is closedthrough contacts 46 for the operating coilot relay5ll or throughcontacts 49 for the operating coil of relay 5I.

When either relay 50 or 5I .of the mot or operat f proximately 'ze that.-'n'orr'nall'y ,"openfcontacts of relay 63 are a closed and the nlormaly jclc'sed contacts are ofjpilot. motor I9 'ed rheo A i l 8 isftran'sfe'rred giilat r12 5' to reactive volt- I andfthe high speedconcred inoperative through ac t $i i5 .otf; 'relayj3. Forf'theidera'tionj for the Operating opened; whereby the "cont? the opening ormore detailed' .c

cycle,' itgjw'll be assumed that "generator winding 2 is over aded andthat rel y 43' is picked up.

.With the c'losurjej ofz r'elay' 'and' consequently relay 50' a circ'uitis completed for notching relays'h-iltl 'ndfQJYwhich efIects astep-by-step control of thei iot' control 19f the res;

(Ifhe relay sfli and I unity powerjact The notch- 'ct teature introducedby the 'not iii 'reiay's and 9| is to'slow up the travel'of theffieldrheostat' I8 so that' the generator willbe able to operate atsubstantially unity'power factor after a predetermined time,

. which for one situation studied has indicated that one minute would besatisfactory. The notching means may make ten to twelve impulses duringthe one minute period. The operating coil of .relay SI 'is' 'energized"from the positive side of bus I5 through the closed contacts 54 of relay50, the closed'co'ntact's 55 'of relay 5I, the closed contacts 92 ofrelay 9b and'then through the closed contacts II of ;jrelay 53 to thenegative node of bus I5] -Th'e'energization of relay SI and closure ofits'conta cts 94 causes the operatpicks up. or if both pick up, thecircuit of alarm 3 device I05 is completedeither throughthe contacts 54of relay 50 or contacts 51 of relay 5I,

giving an indication to the operator of the overload condition of themachine windings.-- If both windings 'of. the generator simultaneouslyexceed thepredetermined value of 55 per cent of current; no action willbe taken-by the load back-01f equipment which is initiated by relays and53 to reduce the generator load and the field excitation. dition is aresult of an operator's action and ing coil ofv relay S0 to beenergizedand this relay picks up 'to cause the operating coil of relay SI to bedeenergized. The time delay dropout of relay SI {through its timedelaydropout means 86, is relatively short. with respect to that of relay 90through its time delay dropout means 93. No

definite time delay relations can be specified for all installations buta given study has indicated thatior one particular installation the timedelay dropout of relay SO rnaybe of the order of five. seconds and thatof relay 9| may be of the order of one-half second 'or longer ifdesired. 7

During the period when relay SI is picked up a, circuit is closedfromthe positive side of bus It is assumed that such cone:

I5 through contacts 95, through the closed contacts 55 of relay 50,through the contacts ll of reactive volt-ampere relay 1.2; the contacts10 otrelay 63, to energize the field winding 21 of" motor-operatedrheostat 18 to lower-the excitation of the generator, ora circuit iscompleted through contacts11 of relay 1.2;.thecontacts 89 of relay 63 tofield winding- Mlofmotor-operated rheostat l8 to raise thefieldexcitation of the generator. Briefly stated, the operationof notchingrelays, 90 and!!! through the contacts of the current responsive relay5.8 or iand the re-- active volt-ampere relay 12' or 1-3 efiects controlwinding of the generator isoverloaded, will causea lowering circuit. tobe made to the governorcontrol motor I12 toeifect a decrease-inpowerin.-

. put to the prime mover-and thereby reduce the load on the prime mover'and-the current of the generator. videdfor this control through thenotehing relays 91 and 98. In studies we have made onone particularinstallation. we have found that it would besatisf'actory to reduce theloadon the overload generator winding in about two minutes time andprovidenotc'hin'g. means; with some fifteen to twenty steps. Theoperation of relays 91 and 98 is similar .tothat of notchingv relays 98and SI. With relay 50 picked up and relay 5-! dropped, out. aspreviously assumed, .a circuit is completed from the positive side ofbus 15, through contacts 53' of relay 58, through the normally closedcontacts v99 of relay 91, through the operating coil of relay 88.,through the contacts 1| of relay 83 (which is latched in) to thenegative side of the bus 15. Relay 98 is then picked up and closes itscontacts N12 to energize the operating coil of relay '91. Relay 91-picks up and deenergizes the operating coil of relay 88, but since relay98 has ,a time delay opening mechanism it maintains its normally opencontacts closed for its time delay period. During the time that relay 98is picked up, its contacts I43 are closed so that a circuit is completedfor the field winding l3 of governor motor I2 from the positive side ofbus 15, through contacts Hi3 through contacts 53 of relay 50 to reducethe power input to the prime mover and thereby reduce the current of theoverloaded generator winding in increments due to the notching action ofrelays 91 and 98.

As previously explained, the relays 84' and 85 are provided to obviatedifficulties which might be occasioned by load swings. These relays areauxiliary to the control efiected by the auxiliary overcurrent relays 50and 5| in connection with the control of the governor control motor l2.

With the apparatus described exclusive of the relays 84- and 85, theregulating relays 43 and 41 only cause the motor I! to lower. Under thiscondition, if load swings occur during this disturbance there would be atendency for the -relays 43 and 41 to lower motor l2 at the peak of eachload swing and, therefore, may cause the turbine and generator to beunloaded below the desired load point. By the addition of relays 84 and85- in the raising circuit of motor 12, raising impulses are given tothemotor I2 at the low point of each swing cycle. Eventually,

of course, the load swings will cease and when steady state conditionsare restored, it will be A notching. featurehas been pro-- seenthatthemotor I2 should come to-a position corresponding to the desiredloading value on the more highly. loaded windingof themachine. Under-theassumed conditions withrelays 84 and 85 functioning, overcurrent relay43 is picked up and relay 84 is, therefore, in the dropout position withits contacts open. Relay 85. however, would be picked up since. relay 41is deenergized. Upon the occasion of load. swings causing. relays 84 and85: to be picked up. Simui-- taneously, a circuit is completed throughthe series-relatedcontacts 86: of relay .84 and contacts 88 of relay 85to provide-a control circuit to operate notching relays 91 andl98 inaddition to the control of these relays effected througheither relay 50or relay 5|. During the time relay 98 is picked up and relays 84 and 85'are; simultaneously closed, a circuit is completed to-energiz'e thefield winding l4 of governor pilot motor 12 and increase the power inputto the prime mover. Thus, the relays 84 and 85 cause raising of thesetting of the governor control mechanism ll. Thus, with the operationof relays 84 and. 85 in cooperation with the operatio'nof redeterminedvalue, theload and field. control is immediately stopped and thegenerator. continues to operate at the final fixed field and governorsetting. until the equipment is reset bythe operator. The operatorresets the equipment by unlatching the mechanism 64 .so. that relay 8.3returns to its deenergized position. This again transfers the controlof: the generator field excitation to the voltage regulator-25andgtransfers the control of the governor controlmotor 12 to themanually operated control switch. I05.

From the foregoing description of the operation when generator winding2is overloaded, it is believed that those skilled in the art willreadily understand the operating cycle wherr g.enerator winding 3 isoverloaded and no further.- description-is believed to be necessary.

While we have shown and described a'particular embodiment of ourinvention, it will be obvious to those skilled in the art that changesand modifications may be made without departing from our invention andwe, therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and-scope of our invention.

What we claim as new andldesire to secure by Letters Patent of theUnited States is:

1. In combination,- an alternating current dynamo-electric machine, anexcitation circuit for said machine regulating means for varying theenergization of said excitation circuit, means responsive to the voltageof said machine for controlling said regulating means, means responsiveto the powerfactor of said machine for controlling said regulatingmeans, and means responsive to an electrical condition of said machinefor selectively placing said regulating means under the control of saidvoltage responsive means or saidpower factor responsive means. I

2. In combination, an alternating current dynamo-electric machine,meansfo-r regulating the excitation of said machine, a voltageresponsive means for controlling said excitation regulating means, powerfactor responsivemeans for controlling said excitation regulating means,means responsive to the current of said machine for selectively placingsaid regulating means under the control of said voltage regulatorresponsive means or said power factor responsive means, and means foreifccting intermittent control of said excitation controlling meansduring operation under control of said power factor responsive means.

3. In combination, an alternating current dynamo-electric machine, anexcitation circuit for said machine, regulating means for varying theenergization of said excitation circuit, means responsive to the voltageof said machine for controlling said regulating means, means responsiveto the reactive volt-amperes of said machine for controlling saidregulating means, and, means responsive to current in said machine belowa predetermined value for placing said regulating means under control ofsaid voltage responsive means and responsive to current in said machine.above a predetermined value for transferring control of said regulatingmeans from saidvoltage responsive means to said means responsive toreactive volt-amperes of said machine.

4. In combination, an alternating current dynamo-electric machine, anexcitation circuit for said machine, regulating means for varying theenergization of said excitation circuit, means responsive to the voltageof said machine for controlling said regulating means, means responsiveto the reactive-volt amperes of said machine for controlling saidregulating means, said voltage responsive means being arranged tocontrol said regulating means for current values of said machine below apredetermined value, means responsive to the current of said machineabove said predetermined value for transferring control of saidregulating means to said reactive volt-ampere responsive means, andmeans for delaying the operation of said last mentioned means untilcurrent values above said predetermined value exist for a predeterminedtime.

5. In an electrical system, an alternating current generator, anexcitation circuit for said generator, means responsive to the voltageof said generator for controlling the energization of said excitationcircuit for generator currents below a predetermined value to maintainthe voltage of said generator at a predetermined 'value, and meansresponsive to current in said generator above said predetermined valuefor controlling said excitation circuit to maintain the reactive currentof said generator at substantially zero.

6. In an electrical system, a double-winding alternating currentgenerator having a pair of separately insulated armature windings andbeing provided with a single rotor, an excitation circuit for saidrotor, regulating means for controlling the energization of saidexcitation circuit, means responsive to the voltage of said generatorfor controlling said regulating means to regulate the voltage of saidgenerator, and means responsive to the current of said windings andoperative when the current in any one winding is above a predeterminedvalue and the current of the other winding is below said predeterminedvalue for controlling said excitation circuit to maintain the reactivecurrent of said generator at substantially zero.

7. In an electrical system, a double-winding alternating currentgenerator having a pair of separately insulated armature windings andbeing provided with a single rotor, an excitation circuit for saidrotor, regulating means for controlling the energization of saidexcitation circuit, means responsive to the voltage or said generatorfor controlling said regulating means, means responsive to the powerfactor of each one of said armature windings, and means responsive tothe current of said armature windings and operative when only one ofsaid windings is traversed by current to transfer the control of saidregulating means from said voltage responsive means to said power factorresponsive means associated with the armature winding traversed bycurrent for maintaining the power factor of said machine atsubstantially unity power factor.

8. In an electrical system, a double-winding alternating currentgenerator having a pair of separately -insulated armature windings andbeing provided with a single rotor, an excitation circuit for saidrotor, regulating means for controlling the energization of saidexcitation circuit,

current responsive means associated with each.

one of said armature windings and each being arranged to be operated toa control position when the current inits associated armature windingexceeds a predetermined value, means responsive to the reactivevolt-amperes of said generator for controlling said regulating means,and means operative in response to the operation of only one of saidcurrent responsive means to its control position for placing saidregulating means under the control of said reactive voltampereresponsive means.

9. In an electrical system, a. double-winding alternating currentgenerator having a pair of separately insulated armature windings andbeing provided with a singl rotor, an excitation circuit for said:rotor, regulating means for controlling the energization of saidexcitation circuit and comprising slow and fast means for raising andlowering the excitation of said generator, means responsive to thevoltage of said generator for controlling said regulating means, meansresponsive to .the reactive volt-amperes of said generator forcontrolling said regulating means, means responsive tocurrent above apredetermined value in either one of said armature windings when currentin the other winding is below said predetermined value for transferringcontrol of said regulating means from said voltage responsive means tosaid reactive volt-ampere responsive means, means controlled by theoperation of said last mentioned meansfor rendering the fast means ofsaid regulating means inoperative, and means for effecting intermittentoperation of said slow regulating means during operation under controlof said reactive voltampere responsive means.

10. In an electrical system, an alternating current generator, means forcontrolling the voltage of said generator, means for controlling thepower factor of said generator, means responsive to apredeterminedelectrical condition of said generator for transferring control of saidgenerator from said first mentioned means to said second mentionedmeans, and means responsive to the current of said generator andoperative when said generator is under control of said second mentionedmeans for controlling the kilowatt output of said generator.

LEO H. PERRY.

. HERMAN BANY.

